This invention relates to a Hall-effect sensor arrangement and more particularly to a Hall-effect sensor particularly suitable for use in a rotational position detector for an internal combustion engine.
FIG. 1 is a schematic sectional side view of the main portion of a conventional Hall-effect magnetic sensor arrangement used in a rotational angular position detector for an internal combustion engine. It is seen that the Hall-effect magnetic sensor element 1 is held by a molded sensor frame 2. In a gap 2a defined between the sensor frame 2 and the sensor element 1, a soft filler material 3 such as a gell material of silicone gell for example is filled in order to protect the sensor element 1 from any mechanical force acting on the sensor element 1 and against any corrosive gas. While the sensor element 1 contains therein a neccessary circuit and the like for a proper sensor function in the form of a hybrid IC circuit, the detailed explanation thereof is omitted because the sensor element 1 may be any suitable well-known commercially available element. It is also seen that a magnet is mounted on a magnetic central axis A of the sensor element 1 with a magnetic gap B between the magnet 4 and the sensor element 1 in order to generate a magnetic field needed by the sensor element 1.
With the above sensor arrangement of the conventional design, an unillustrated magnetic flux shutter attached to a moving member may be used so that it moves in the direction perpendicular to the plane of the figure through the gap B between the magnet 4 and the sensor element 1, whereby the rotational position, the rotational angle, displacement, etc. can be detected through the measured change in the magnitude of the magnetic flux passing through the Hall-effect sensor element 1. The Hall-effect magnetic sensor as described above may be advantageously used in an internal combustion engine distributor as a rotational angle detector for a crank shaft of an internal combustion engine.
In the conventional Hall-effect magnetic sensor arrangement as described above, the magnet 4 is supported and covered at its side face 1a facing toward the pole face 4a of the magnet 4 by a molded resin material wall 2b of the sensor frame 2 which has a relatively large thickness t. This wall thickness t must be relatively large because of the neccessary mechanical strength of the wall 2b, so that the distance L1 between the magnetic pole face 4a of the magnet 4 and the side face 1a of the sensor element 1 must inevitably be large, resulting in a poor signal accuracy.